The present invention relates to technologies of restraining the operation of an actuator suspension assembly when a rotary disk storage device such as a magnetic disk device or an optical magnetic disk device is in non-operation and a head/slider is at a predetermined retracted position, and releasing the actuator suspension assembly from the restrained state when the storage device is in operation. More specifically, the invention relates to a technologies of restraining and releasing the operation of an actuator suspension assembly securely with use of a simple mechanism within a small space defined inside a rotary disk storage device.
A magnetic disk device includes a rotary magnetic disk having a magnetic layer formed on a surface thereof and adapted to rotate about a spindle shaft, an actuator suspension assembly, and a control unit for controlling read and write of data and for controlling the operation of the actuator suspension assembly. The actuator suspension assembly includes a head for read and write of data, a slider with the head attached thereto and for providing an air bearing surface (ABS), a suspension assembly with the slider attached thereto, and a carriage arm to which the suspension assembly is connected and which is adapted to turn about a pivot shaft.
A coil arm is formed in part of the carriage arm to hold a voice coil. The coil arm is disposed within a magnetic field of a voice coil magnet. The voice coil magnet and the voice coil constitute a voice coil motor (VCM) which generates a driving force for turning the carriage arm.
With rotation of the magnetic disk, an air current on the surface forms an air bearing and a lift force is imparted to an air bearing surface of the slider, so that the slider is lifted slightly from the surface of the magnetic disk. With the driving force of the voice coil motor, the slider turns about the pivot shaft substantially radially of the magnetic disk while floating slightly from the surface of the magnetic disk, thereby permitting the head to read or write data from or to a predetermined position on the disk surface.
There is a recent tendency that a magnetic disk device is mounted on a portable information device such as a portable computer. Thus, both the reduction of size and the improvement of impact resistance are required. When the magnetic disk device is at rest, the magnetic disk does not rotate, so that the air bearing vanishes. In a load/unload type magnetic disk device, while the rotation of a magnetic disk comes to a halt, a slider is retracted to a retraction mechanism called ramp which is provided outside the magnetic disk. The ramp is described, for example, in Japanese Patent Laid-open No. 11-110933.
With the slider retracted to the ramp, if an impact force is applied to the magnetic disk device from the exterior, causing the slider to move to a recording area of the magnetic disk and come into contact with the disk surface, either the slider or the magnetic disk may be damaged. It is necessary to eliminate such damage.
If the slider lands on the surface of the magnetic disk which is at rest, there arises a sticking phenomenon called stiction between the air bearing surface of the slider and the magnetic disk surface. In the state of stiction, if an attempt is made to rotate the magnetic disk, the magnetic disk surface may be damaged or in the worst case it may become impossible to start up the magnetic disk.
In the magnetic disk device, therefore, it is necessary to use a mechanism which, after the slider has been moved to its retracted position, restrains the slider firmly at the retracted position until re-rotation of the magnetic disk even if a large impact force is applied to the magnetic disk device. Further, it is necessary that the restraint be released immediately for re-start-up of the magnetic disk, thereby allowing the actuator suspension assembly to operate freely.
Examples of methods for restraining the actuator suspension assembly while the slider is in its retracted position include magnet type, electromagnetic solenoid type, and inertial latch type methods that are described in Japanese Patent Laid-open No. 8-339645. According to the magnet type method, it is necessary that, after a carriage arm of the actuator suspension assembly is once attracted by a magnet, the actuator be operated for unlocking. A limit is encountered in the magnitude of attractive force. Besides, to obtain a large magnetic field intensity, it is necessary to ensure a large space for a large magnet. Thus, with the magnet alone, it has so far been difficult to cope with a large impact force. See Japanese Patent Laid-open No. 8-339645.
The electromagnetic solenoid type is disadvantageous in that the structure becomes complicated. Further, since the inertial latch has a play in operation, sound is generated during carriage, resulting in a user feeling as if an inside component had fallen off. Examples of other methods include a technique which utilizes an eddy current disclosed in U.S. Pat. No. 6,462,913.
According to the technique disclosed in the above U.S. patent, a rotary disk provided with a hook and magnet for locking an actuator is attached to a base of a housing rotatably, and when the rotation of a spindle is at rest, the rotary disk is placed in a hook position by virtue of a magnetic action induced by the magnet and a magnetic material formed on the back side of a hub, while when the spindle is rotating, the rotary disk is rotated with a force of an eddy current exerted on the magnet which eddy current is developed in the hub, to unlock the actuator.